1. Field of the Invention
The present invention relates to a one-way clutch of roller type used as a part such as a torque transmitting element or a back stopper in a driving apparatus of a motor vehicle, an industrial machine and the like, for example.
2. Related Background Art
In general, a one-way clutch of roller type is comprised of an outer race having at least one pocket provided at its inner periphery with a cam surface, an inner race disposed in concentric with the outer race and having an outer peripheral track surface, a roller disposed in the pocket and adapted to transmit torque between the outer peripheral track surface of the inner race and the inner peripheral cam surface of the outer race, and a spring contacted with an idle rotation side of the roller.
With this arrangement, in the one-way clutch of roller type, the inner race is designed so as to be rotated only in one direction with respect to the outer race by means of a cam mechanism constituted by the roller and the cam surface. That is to say, the inner race is designed so that it is idly rotated relative to the outer race in one direction, and on the other hand, it applies rotational torque to the outer race via the cam mechanism only in an opposite direction.
For example, in many cases, since a one-way clutch used as a starter of a motor bike is used under a high speed rotation and severe vibration environment and an environment including a large amount of powder dust, foreign matters such as dust including worn powder are apt to be accumulated in the one-way clutch. Since the foreign matters accumulated in the one-way clutch affect a bad influence upon engaging performance, it is desirable to remove the foreign matters promptly in order to enhance reliability of the one-way clutch.
On the other hand, in some one-way clutches of roller type used as the starter of the motor bike, as disclosed in Japanese Patent Application Laid-open No. 5-044615 (1993), by providing side plates on both sides of an outer race of the one-way clutch, rollers used in the one-way clutch and springs for biasing the springs are prevented from being dislodged.
Further, in order to enhance the performance of the one-way clutch, it has been proposed to lubricate the members. For example, the above-mentioned Japanese Patent Application Laid-open No. 5-044615 (1993) discloses an arrangement in which a one-way clutch is lubricated by oil. Further, some one-way clutches have been used under a dry condition without oil lubrication.
However, when the one-way clutch as disclosed in the above-mentioned Japanese Patent Application Laid-open No. 5-044615 (1993) is used under a severe vibration environment and an environment in which it is hard to lubricate the one-way clutch, since the side plates are attached to the both sides of the outer race, foreign matters such as dust including worn powder accumulated in the clutch are hard to be discharged, and, the dust accumulated in the clutch affects a bad influence upon operations of rollers and springs, which may causes wear of the rollers, thereby worsening the reliability of the one-way clutch.
Further, since the side plates must be secured to the both sides of the outer race and holes or recesses for housing the springs must be formed in the outer race, the number of manufacturing steps is increased, thereby increasing a manufacturing cost.
Further, in a case where the one-way clutch is used in a motor bike subjected to the severe vibration, if a cage may be rotated relative to the outer race, the cage may be rotated in an undesirable direction with respect to the pockets of the outer race, thereby affecting a bad influence upon engaging performance of the one-way clutch.
In this way, in the one-way clutch used as the starter of the motor bike having the side plates, it is desired to provide a one-way clutch of roller type in which the engaging reliability can be maintained and the cost is reduced, even under the high speed rotation and severe vibration condition and a service condition in which it is hard to lubricate the one-way clutch and the foreign matters such as the dust including the worn powder are apt to be accumulated.